1. Field of the Invention
The present invention relates to a technology for controlling wireless connection between a mobile terminal and a plurality of base stations.
2. Description of the Related Art
When there is a heavy rain or a flood, road conditions are monitored to check whether the roads are flooded or caved in.
One approach is to mount a video camera on a car and take videos of the road and transmit the videos real-time to a management center where a person can make decisions about the road conditions. Generally, such videos are transmitted from a mobile terminal mounted on the vehicle to a base station by wireless communication, and the base station transmits the video to the management center by wireless or cable communication. Because the mobile terminal mounted on a car and the car is moving, a relative position of the mobile terminal and the base stations change with time, and therefore, a roaming technology needs to be employed.
When the mobile terminal moves out of an area of one base station, the mobile terminal switches the wireless connection to another nearest base station. A conventional technology has been disclosed in Japanese Patent Application Laid Open No. H11-331941.
However, when the wireless connections are switched, some data is lost so that communication is interrupted. Data is lost during the time from when communication with earlier base station is cut and when communication with the next base station is established. Accordingly, if the car is moving fast, wireless connections are switched more frequently, and therefore, communication is interrupted often. The problem of interruption in communication becomes severe when large amount of data are to be transmitted.